BIOL 005B Lecture Notes - Lecture 23: Cork Cambium, Meristem, Vascular Cambium
BIOL 005B Lecture 23: Plant Growth and Development
●Meristems: Where the growth occurs
○Meristems are perpetually embryonic tissue and allow for indeterminate growth
(a few plants exhibit determinate growth - rare)
○Apical meristems are located at the tops of roots and shoots and at the axillary
buds of shoots
○Apical meristems elongate shoots and roots, a process called primary growth
○Lateral meristems add thickness to woody stems, a process called secondary
growth
○There are two lateral meristems: the vascular cambium and the cork cambium
○The vascular cambium adds layers of vascular tissue called secondary xylem
(wood) and secondary phloem
○The cork cambium (in stems/trunk) replaces the epidermis with periderm, which
is thicker and tougher
●Primary Growth: Roots
○The root tip is covered by a root cap, which protects the apical meristem as the
root pushes through soil
○Growth occurs just behind the root tip, in three zones of cells:
■Zone of cell division
■Zone of elongation
■Zone of maturation
○The vascular system of a root or a stem is known as the stele
○In angiosperms - the stele of the root is organized into a vascular cylinder
○The primary growth of roots produces the epidermis, ground tissue, and vascular
tissue
○The ground tissue fills the cortex, the region between the vascular cylinder and
epidermis
○The innermost layer of the cortex is called the endodermis
○Lateral roots arise from within the pericycle, the outermost cell layer in the
vascular cylinder
●Primary Growth: Shoots
○A shoot apical meristem is a dome-shaped mass of dividing cells at the shoot tip
○Leaves develop from leaf primordia along the sides of the apical meristem
○Axillary buds develop from meristematic cells left at the bases of leaf primordia
●Tissue organization of stems
○Lateral shoots develop from axillary buds on the stem’s surface
○In most eudicots, the vascular tissue consists of vascular bundles that are arranged
in a ring
○In most monocot stems, the vascular bundles are scattered throughout the ground
tissue, rather than forming a ring
●Tissue organization of leaves
○Epidermis reduces water loss
○Stomata allow CO2 exchange between the air and the photosynthetic cells in a
leaf
Document Summary
Biol 005b lecture 23: plant growth and development. Meristems: where the growth occurs buds of shoots (a few plants exhibit determinate growth - rare) Meristems are perpetually embryonic tissue and allow for indeterminate growth. Apical meristems are located at the tops of roots and shoots and at the axillary. Apical meristems elongate shoots and roots, a process called primary growth. Lateral meristems add thickness to woody stems , a process called secondary. There are two lateral meristems: the vascular cambium and the cork cambium. The vascular cambium adds layers of vascular tissue called secondary xylem. The cork cambium (in stems/trunk) replaces the epidermis with periderm , which (wood) and secondary phloem growth. The root tip is covered by a root cap , which protects the apical meristem as the. Growth occurs just behind the root tip , in three zones of cells: root pushes through soil is thicker and tougher.
